Dinopedia:Tyrannosaurus rex
Killer Instinct There has been ongoing debate as to how Tyrannosaurus found its food. Most people believe it was a predator, down and killing its food in the same way lions do. However, others believe it was a scavenger, as evidenced by its large olfactory bulbs (which indicate a phenomenal sense of smell). The best possible conclusion is that T. rex ''was both a part time hunter and scavenger, since no carnivore relies on just one of those things alone. Evidence has shown that ''T. rex was also cannibalistic when the sitiuation demanded it, or after killing its own kind for mating or territory. There's also evidence that Tyrannosaurus rex ''hunted in groups, from when Phil Currie found a large number of ''Tyrannosaurus' close, more primitive relative Albertosaurus ''in Canada that were all of different ages, and since ''Albertosaurus, which was more primitive and not as smart as its more famous cousin, hunted in groups, then why shouldn't T. rex have done the same? The concept that makes Tyrannosaurus rex so deadly is that it had a huge 4.5-5 ft (1.4-1.5 m) long skull that weighed well over 1,000 lbs. (454.5 kg.) in weight and great jaws that could dislocate like a snake to swallow large pieces of meat. It also banana-sized teeth (13 in. or 34 cm), some of the largest in the animal kingdom, and could bite 500-600 lbs. (227-273 kg.) of meat off at a time and swallow it whole, sometimes breaking the teeth off when biting but growing them back repeatedly. Unlike most predators, T. rex would also eat basically the whole carcass, bones and all. We know because we've found Tyrannosaurus coprolites (fossilized poop) with ceratopsian and hadrosaur bones in it. The teeth made Tyrannosaurus different from most predators, because these teeth were blunter, stronger, and more suited to crush bone and penetrate armor instead of slice through flesh. Another discovery seems to show that T. rex also had a very infectious bite from the teeth, since the serrations in the them were much larger than other theropoods, and probably held pieces of rotten meat in them, which allowed harmful bacteria to grow and cause disease when the Rex bit down on prey items, so even if the'' T. rex'' didn't get the kill on the first bite, the prey would eventually die of infection and the T. rex ''would just track it down using its keen sense of smell and eat it after it'd died or became too weak to fight. It also seems as though ''T. rexes in the North fought against Triceratops, Ankylosaurus, Edmontosaurus, and Pachycephalosaurus, while ones in the South fought against all of those plus a large sauropod called Alamosaurus. The average bite force of Tyrannosaurus rex astounded scientists when they used calculations from crocodile bite forces to find out that Tyrannosaurus rex had a bite force of 60,000 newtons (6.8 tons) of pressure and perhaps even more. Higher estimates were made by professor Mason B. Meers of the University of Tampa in 2003. In his study, Meers estimated a possible bite force of around 183000 to 235000 newtons or 18.3 to 23.5 metric tons; a bite force equivalent to that of the largest Megalodon shark specimens. Other studies say the neck could lift 5 tons. This tremendous amount of force is enough to easily crush bone and bite through and bend a ste el oil drum, and also is by far the most powerful bite force of any terrestrial animal that ever lived, surpassing any modern-day animal, such as sharks, crocodiles, or hippos. Tyrannosaurs could probably use hunting tactics which required lunging at prey from short distances, and then crushing them with its jaws. It also could break bones with it's tail, teeth, and could also do so by ramming into prey with its rock-hard head. T. rex was also the most muscularly built theropod ever, even its tiny arms were strong, being able to lift 500 lbs. (227 kg.) with each arm, crushing any Olympic record for weight-lifting. The exact use for its arms are unknown, but most scientists agree it was to grab onto struggling prey with those 2-inch (5-cm.) long, hook-like claws while its huge jaws finished it off with a bite to the neck. They also could've been used to grab on at first while mating or to help lift itself up off the ground. Most scientists agree that T. rex's arms got so small throughout evolution from its jaws becoming so big and powerful, so the arms were less needed, and if T. rex hadn't gone extinct, the arms might've completely disappeared all together. Although it was the top predator, Tyrannosaurus rex had a very tough life, most not even living past their early 30's (even Sue died at 29), but T. rex has proven to also be a very resilient dinosaur. Nearly every adult Tyrannosaurus specimen found has wounds that it have been healed, but would've killed nearly any other animal. For instance, in one specimen named Sue, it had suffered and survived injuries such as broken ribs, infections in the vertebrae and legs, and also had arthritis. Other specimens have also been healed from Triceratops horns, Ankylosaurus clubs, and even bitemarks from other tyrannosaurs. In fact one specimen nicknamed Stan even had a piece of the back of his skull and brain case bitten out of and he still lived for several more years. Aside from fighting some of the toughest herbivores that nature's ever produced, like Triceratops and Ankylosaurus, they also fought amongst themselves frequently. Nearly every complete or mostly complete skull found has bite marks from the only large theropod around, another T. rex. They most likely fought over mates, territory, or food. Tyrannosaurus and its cousins were so successful that whenever a tyrannosaur moved into a territory, it drove out any other large predator, and were soon the only large predators in the area. T. rex's speed has been a topic of discussion for a while. The scientists that believe T. rex was a scavenger say that it was a slow-moving, lumbering animal that could barely run 15 mph. However, some speculate, that since T. rex had some of the longest and most muscular legs of any bipedal dinosaur, it was a fast runner. In fact its legs and pelvis alone made up half of the tyrant lizard's body weight, and the tail alone weighed a full ton, designed to hold extra muscle mass and counter-balance its enormous head. Another study on the famous Tyrannosaurus ''specimen nicknamed Sue also shows deep indentations on the leg bones where muscle once was, suggesting high concentration of the tissue. Also, unlike most other large theropods, ''T. rex had a longer shin bone than a femur bone, giving it an ostirich-like build and shows that T. rex possibly was fairly fast. Scientists that believe T. rex was a predator say that it could run 25-28 mph (40-45 km/h), faster than Olympic sprinters! Even if T. rex wasn't that fast, studies seem to show that T. rex was faster than most of its prey items. It also seems as though if T. rex was a predator, than it held its prey down with one of its feet, using the other one and its long tail for balance, and then taking a bite out if its prey's neck, severing the spine. T. rex also likely had specialized pads on the soles of its feet like elephants today to feel low frequencies in the ground to find and locate its prey like ceratopsians or ankylosaurs. A study by Eric Snively and Anthony P Russel published on 2003 would also find that the tyrannosaurid arctometatarsals and its elastic ligaments worked together in what he called a 'tensile keystone model' to strengthen the feet of Tyrannosaurus, increase the animals stability and add greater resistance to dissociation over that of other theropod families; while still allowing resiliency that is otherwise reduced in ratites,horses, giraffids and other animals with metapodia to a single element. The study would also point out that elastic ligaments in larger vertebrates could store and return relatively more elastic strain energy, which could have improved locomotor efficiency and decrease the strain energy transferred to the bones. The study would suggest that this mechanism could have worked efficiently in tyrannosaurids as well. Hence, the study involved identifying the type of ligaments attached to the metatarsals, then how they functioned together and comparing it to those of other theropods and modern day analogs. The scientists would find that arctometatarsals may have enabled tyrannosaurid feet to absorb forces such as linear deceleration, lateral acceleration and torsion more effectively than those of other theropods. It is also stated in their study that this may imply, though not demonstrate, that tyrannosaurids such as Tyrannosaurus had greater agility than other large theropods without an arctometatarsus. A study in 2007 used computer models to estimate running speeds, based on data taken directly from fossils, and claimed that Tyrannosaurus rex had a top running speed of 8 metres per second (29 km/h; 18 mph). An average professional football (soccer) player would be slightly slower, while a human sprinter can reach 12 metres per second (43 km/h; 27 mph). Muscle mass reconstruction of M. caudofemoralis longus. However in 2010, Scott Persons, a graduate student from the University of Alberta proposed that Tyrannosaurus's speed may have been enhanced by strong tail muscles.105He found that theropods such as T rex had certain muscle arrangements that are different from modern day birds and mammals but with some similarities to modern reptiles.106 He concluded that the caudofemoralis muscles which link the tail bones and the upper leg bones could have assisted Tyrannosaurus in leg retraction and enhanced its running ability, agility and balance. The caudofemoralis muscle would have been a key muscle in femoral retraction; pulling back the leg at the femur.105 The study also found that theropod skeletons such as those of Tyrannosaurus' had adaptations (such as elevated transverse processes in the tail vertebrae) to enable the growth of larger tail muscles and that Tyrannosaurus's tail muscle mass may have been underestimated by over 25 percent and perhaps as much as 45 percent. The caudofemoralis muscle was found to comprise 58 percent of the muscle mass in the tail of Tyrannosaurus. Tyrannosaurus also had the largest absolute and relative caudofemoralis muscle mass out of the three extinct organisms in the study. This is because Tyrannosaurus also had additional adaptations to enable large tail muscles; the elongation of its tail's hemal arches. According to Persons, the increase in tail muscle mass would have moved the center of mass closer to the hind quarters and hips which would have lessened the strain on the leg muscles to support its weight; improving its overall balance and agility. This would also have made the animal less front heavy, thus reducing rotational inertia. Persons also notes that the tail is also rich in tendons and septa which could have been stores of elastic energy, and thereby improved locomotive efficiency. Persons adds that this means that non-avian theropods actually had broader tails than previously depicted, as broad or broader laterally than dorsoventrally near the base. Heinrich Mallison from Berlin’s Museum of Natural History would also present a theory on 2011, suggesting that Tyrannosaurus and many other dinosaurs may have achieved relatively high speeds through short rapid strides instead of the long strides employed by modern birds and mammals when running, likening their movement to power-walking. This, according to Mallison, would have been achievable irrespective of joint strength and lessened the need for additional muscle mass in the legs, particularly at the ankles. To support his theory, Mallison assessed the limbs of various dinosaurs and found that they were different from that of modern mammals and birds; having their stride length greatly limited by their skeletons, but also having relatively large muscles at the hindquarters. He would however find a few similarities between the musculature of dinosaurs and race-walkers; having less muscle mass in the ankles but more at the hindquarters. Mallison suggests that the differences between dinosaurs the extant mammals and birds would also have made equations to calculate speed from stride length inapplicable to dinosaurs. John Hutchinson however advised caution regarding this theory, suggesting that they must first look into dinosaur muscles to see how frequently they could have contracted. Another terrifying aspect about Tyrannosaurus rex was the size of its brain. It was the smartest of the large theropods, and its brain was about the size of a gorilla's or a coconut. Recent studies show that T. rex was probably about as smart as a lion, meaning this dinosaur could use strategic thinking to take down tough prey like Triceratops and Ankylosaurus. T. rex ''probably became so smart because unlike other large theropods, which hunted large, small-brained sauropods, it hunted tough animals that were about the same size, like ''Triceratops, so it would need to come up with a plan to kill it. That can also explain why the teeth were so much broader, thicker, and stronger than other carnivores, since there was more armor that needed to be bitten through. This brain size may also have led T. rex ''to be able to form a family pack, letting the juveniles chase after the prey items into the jaws of the adults, like lions do today. Hunting in packs or pairs could also be a factor in bein g able to take down tough prey. If ''T. rex ''hunted in a pack, most likely the juveniles would chase the prey towards the more powerful adults, where they would kill it. If it hunted in pairs, they probably attacked together on each side. If it was alone, the tyrannosaur probably waited in ambush until it was ready to attack, and then would charge and repeatedly bite down until thge prey became weak and died. The large brain also helped ''T. rex take better care of its young, so the next generation of killers had a greater chance of surviving. The skull of T. rex also shows that it had large eyes that faced forward, giving it three-dimensional binocular vision, while most theropods had eyes that were on the sides of their heads. Considering how large its eyes were and how good of a sense of smell it had, there's also been debate as to whether Tyrannosuarus was a part-time nocturnal hunter. Taxonomy For a long time T. rex was considered part of the carnosaur genus, like Allosaurus, but a closer analysis a few years ago showed that it was actually part of its own genus; the tyrannosaurids, which descended from coelurosaurs like Velociraptor. While'' Tyrannosaurus was by far the biggest tyrannosaurid, it wasn't the only one. It had numerous relatives; [[Daspletosaurus|''Daspletosaurus]], ''Albertosaurus'', and ''Tarbosaurus'' are all part of the tyrannosaur family. The earliest known tyrannosaurs were actually small hunters from the Jurassic Period, like Guanlong. Of all it's relatives, ''Daspletosaurus'' is believed to be the direct ancestor of T. rex, ''due to its very similar appearance. The skull of a small tyrannosaur, ''Nanotyrannus, found in South Dakota, was later thought to be from an adolescent T. rex ''but it is still possibly a separate species or genus. ''T. rex had a relatively short neck for such a large theropod, but was very well muscled and designed to withstand much more force from its powerul bite than other theropods were. Although Tyrannosaurus rex was the peak of tyrannosaur and carnivourous dinosaur evolution, it was an evolutionary dead end, with its closest descendants being birds, because of the K-T Extinction caused by a massive asteroid or comet. Of the 31 specimens found, the most famous, most complete, and largest T. rex ''skeleton on display is Sue, a 42 foot (13 m) long ''Tyrannosaurus found in the badlands of South Dakota in 1990 by Susan Hendrickson. Sue's the most complete skeleton of any tyrannosaur, and was auctioned off in Washington D.C. for over $8,000,000. The skeleton is now on display in the Field Museum in Chicago, Illinois for everyone to see, but its skull is on a seperate case because it was too heavy to put on the actual skeleton, so they made a lighter replica and put it on the frame instead. Sue was named after the paleontologist who found it, but scientists aren't quite sure what its gender is. Not only is Sue the most complete and largest displayed T. rex, but it's also the oldest, dying at the age of 28. This seems to suggest tyrannosaurs grew continuously as they aged. Sue has given the most information of any T. rex skeleton yet, and is one of only a few Tyrannosaurus with a complete skull and forelimb. Despite being so large and ferocious, Sue's bones have shown just how tough its life was. It has healed rib fractures, healed infected broken leg bones, bites taken out of its vertebrae by other tyrannosaurs, and even arthritis. Another significant specimen found by Dr. Jack Horner, curator of the Museum of the Rockies in Bozeman, Montana, shows medullary tissue in the bone sctructure, tissue only found in modern-day pregnant birds. This is a very significant find because it's the first dinosaur ever discovered to show that dinosaurs (or at least coelurosaurs) had a birth cycle much closer to birds than previously thought, and also shows the first proven male or female Tyrannosaurus. Some other famous T. rex specimens are Stan, Thomas, Samson, and Jane. Popular Culture *''Tyrannosaurus'' is possibly the most famous of dinosaurs, ever since its discovery in 1902, it's been extremely popular, and it's almost always the first dinosaur that comes to mind when the word "Dinosaur" is mentioned and is one of the only dinosaurs where nearly everyone actually fully knows its name. *It's shown in many recent movies involving dinosaurs. Its first appearance in the movies was in the 1925 film The Lost World, ''where it battles an ''Agathaumas. *It also played an important role in the famous movie Jurassic Park. *It also appeared in the movies sequel The Lost World: Jurassic Park. ''In this movie it rampaged through San Diego in an attempt to find its offspring. *It later appeared in the third sequel ''Jurassic Park 3. Here a sub-adult male Tyrannosaurus ate the remains of a Parasaurolophus and was killed by a fully grown adult Spinosaurus. * It also starred in an episode of the reknown documentary series Walking With Dinosaurs, and two shows from the same producers called Prehistoric Park ''and Primeval''. *It also appeared in several episodes of the well known documentary Jurassic Fight Club, Animal Armageddon, Dinosaurs Decoded, Truth About Killer Dinosaurs, T. rex: New Science, New Beast, Prehistoric Denver, Dino Gangs, Ultimate Guide: Tyrannosaurus rex, Last Day of the Dinosaurs, and Clash of the Dinosaurs. *Another documentary it's been in is Dinosaur Revolution, ''where it showed how a family of tyrannosaurs lived until the K-T Extinction. *A ''Tyrannosaurus named Heart serves as the main protaganist of the 2010 anime film You Are Umasou ''and as antagonists in the books and TV shows of Dinotopia. *It's also featured in many games involvong dinosaurs, including all Jurassic Park Games, all Dino Crisis Games, and also Primal Carnage. It has also been featured in the Fossil Fighters series, appearing on the cover of the seque, Fossil Fighters Champions. ''Tyrannosaurus ''appears in Turok, as there is a ''T. rex ''that has grown to intense size, as it is nicknamed "Mama Scarface", for the scar on its right eye. *It was also in the IMAX movie, T. rex: Back to the Cretaceous. A giant robotic ''Tyrannosaurus is piloted by the red ranger in both the Mighty Morphin' Power Ranger series and the Dino Thunder series. *''Tyrannosaurus'' is also the antagonist of nearly every episode of The Land Before Time. *It also starred in a Hollywood parody called T. rex: A Dinosaur in Hollywood, where they talk about how T. rex gained its fame throughout its discovery to modern-day movies, and also was in the Disney movie Fantasia where it fought a Stegosaurus while the song "The Rite of Spring" played. *It was also a main source for evolution in many episodes of the History Channel show Evolve. *It also served as the main dinosaur in a documentary called Tyrannosaurus Sex, where they talked about how T. rex and other dinosaurs may have reproduced. *''Tyrannosaurus'' was also an antagonist in the comedy movie Land of the Lost and the Korean film Speckles: the Tarbosaurus, where it was named "One Eye" and killed family of the main character "Speckles", a Tarbosaurus. *Jack Horner also talked about T. rex and why he believes it's mostly a scavenger in Valley of the T. rex. *''Tyrannosaurus'' also made a short cameo in Dinosaur Planet. *A T. rex is the main protagonist of We're Back! A Dinosaur's Story * Gallery Trexprofile.jpg|A Tyrannosaurus profile. Tyrannosaurus rex.jpg|Tyrannosaurus standing in a pond. 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